Xpath query results are always empty

Question

I have the following XML document:

<?xml version="1.0"?>
<GetMatchingProductForIdResponse xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01">
<GetMatchingProductForIdResult Id="B0009VCOU4" IdType="ASIN" status="Success">
    <Products xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01" xmlns:ns2="http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd">
    <Product>
        <Identifiers>
            <MarketplaceASIN>
                <MarketplaceId>ATVPDKIKX0DER</MarketplaceId>
                <ASIN>B0009VCOU4</ASIN>
            </MarketplaceASIN>
        </Identifiers>
        <AttributeSets>
            <ns2:ItemAttributes xml:lang="en-US">
                <ns2:Binding>Electronics</ns2:Binding>
                <ns2:Brand>DOBANI</ns2:Brand>
                <ns2:Feature>Handcrafted Quality, Value Priced</ns2:Feature>
                <ns2:Feature>Satisfaction Guaranteed! 30-Day Return Policy!</ns2:Feature>
                <ns2:ItemDimensions>
                    <ns2:Height Units="inches">7.00</ns2:Height>
                    <ns2:Length Units="inches">6.00</ns2:Length>
                    <ns2:Width Units="inches">6.00</ns2:Width>
                </ns2:ItemDimensions>
                <ns2:Label>Mid-East</ns2:Label>
                <ns2:ListPrice>
                    <ns2:Amount>9.90</ns2:Amount>
                    <ns2:CurrencyCode>USD</ns2:CurrencyCode>
                </ns2:ListPrice>
                <ns2:Manufacturer>Mid-East</ns2:Manufacturer>
                <ns2:Model>BULB</ns2:Model>
                <ns2:PackageDimensions>
                    <ns2:Height Units="inches">3.70</ns2:Height>
                    <ns2:Length Units="inches">8.10</ns2:Length>
                    <ns2:Width Units="inches">4.00</ns2:Width>
                    <ns2:Weight Units="pounds">0.35</ns2:Weight>
                </ns2:PackageDimensions>
                <ns2:PackageQuantity>1</ns2:PackageQuantity>
                <ns2:PartNumber>BULB</ns2:PartNumber>
                <ns2:ProductGroup>Single Detail Page Misc</ns2:ProductGroup>
                <ns2:ProductTypeName>MUSICAL_INSTRUMENTS</ns2:ProductTypeName>
                <ns2:Publisher>Mid-East</ns2:Publisher>
                <ns2:SmallImage>
                    <ns2:URL>http://ecx.images-amazon.com/images/I/31Fsu5jKWsL._SL75_.jpg</ns2:URL>
                    <ns2:Height Units="pixels">75</ns2:Height>
                    <ns2:Width Units="pixels">50</ns2:Width>
                </ns2:SmallImage>
                <ns2:Studio>Mid-East</ns2:Studio>
                <ns2:Title>Spare Rubber Bulb</ns2:Title>
            </ns2:ItemAttributes>
        </AttributeSets>
        <Relationships/>
        <SalesRankings>
            <SalesRank>
                <ProductCategoryId>sdp_misc_display_on_website</ProductCategoryId>
                <Rank>36468</Rank>
            </SalesRank>
        </SalesRankings>
    </Product>
</Products>
</GetMatchingProductForIdResult>
<ResponseMetadata>
    <RequestId>afnapq823haeufabq2rhalhtz</RequestId>
</ResponseMetadata>
</GetMatchingProductForIdResponse>

I am trying to get the package dimensions, but none of my xpath queries work. Have tried these using PHP's built-in xpath functions and using QueryPath 3.0.0, but neither works.

This doesn't work even though XML Tree in Chrome shows it should:

/GetMatchingProductForIdResponse/GetMatchingProductForIdResult/Products/Product/AttributeSets/ns2:ItemAttributes/ns2:PackageDimensions/ns2:Height

I thought neutralizing the namespace would get rid of the problem since the above triggers a namespace error, but it does not:

/GetMatchingProductForIdResponse/GetMatchingProductForIdResult/Products/Product/AttributeSets/*[local-name()='ItemAttributes']/*[local-name()='PackageDimensions']/*[local-name()='Height']

Answer 1

I'm afraid even the first part of your xpath is suffering for the namespace issue. Have you tried :

/*[local-name()='GetMatchingProductForIdResponse']/*[local-name()='GetMatchingProductForIdResult']/*[local-name()='Products']/*[local-name()='Product']/*[local-name()='AttributeSets']/*[local-name()='ItemAttributes']/*[local-name()='PackageDimensions']/*[local-name()='Height']

I think to use the normal xpath approach, you will need to set the corresponding namespaces on the xpath evaluator itsself.

Answer 2

Xpath has no default namespace. The Xpath provided by Chrome is invalid. An Xpath element expression without a namespace prefix always matches elements without a namespace.

You need to register your own namespace prefixes and use them:

$dom = new DOMDocument();
$dom->loadXml($xml);

$xpath = new DOMXpath($dom);
$xpath->registerNamespace(
  'p', 'http://mws.amazonservices.com/schema/Products/2011-10-01'
);
$xpath->registerNamespace(
  'pd', 'http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd'
);

$result = $xpath->evaluate(
  'string(
    /p:GetMatchingProductForIdResponse
    /p:GetMatchingProductForIdResult
    /p:Products
    /p:Product
    /p:AttributeSets
    /pd:ItemAttributes
    /pd:PackageDimensions
    /pd:Height
   )'
);

var_dump($result);

Output: https://eval.in/150409

string(4) "3.70"

Answer 3

    /**
     * Convert XML to JSON and return.
     */
    $response = preg_replace("/(<\/?)(\w+):([^>]*>)/", "$1$2$3", $response);
    $xml = simplexml_load_string($response);
    $json = json_encode($xml);
    return json_decode($json,TRUE);

This worked for me